Downhole operations in oil and gas wells typically involve, among other things, deploying one or more perforating guns into the wellbore to perforate wellbore casing and tubing and surrounding hydrocarbon-bearing formations to liberate and collect oil and gas within the formations. Once a perforating gun is deployed into a wellbore to a desired position, shaped charges that the perforating gun carries are detonated to create the desired perforations. Accordingly, a typical perforating gun includes, among other things, electrical connections for receiving a detonation signal and initiating detonating components such as a detonator and a detonating cord for ballistically detonating the shaped charges. An exemplary perforating gun is described below with reference to FIG. 1.
As shown in FIG. 1, the perforating gun 100 includes a gun carrier 110 having a top end 101 and a bottom end 102 opposite the top end 101. The gun carrier 110 is typically a cylindrical metal body that isolates a charge carrier 141 from, among other things, wellbore fluid that is pumped under high hydraulic pressure into the wellbore to further open the perforations and create further cracks and flow paths in the hydrocarbon-bearing formation for the recovery of oil and gas. The wellbore fluid may damage or render inoperable internal components of the perforating gun 100 or cause premature detonation of shaped charges 142 if the wellbore fluid infiltrates a hollow interior 130 of the gun carrier 110 in which the various internal components are housed. The various internal components of the perforating gun 100 may be arranged as an internal gun assembly 140 including the charge carrier 141. The charge carrier 141 may have a shape and features designed to orient and/or retain the various internal components such as the shaped charges 142, a detonating cord 143, an electrically conductive line/electrically conductive through wire 144, and a ground contact 145 (in FIG. 1, the ground contact is shown as a ground bar). The charge carrier 141 may be, for example, an injection molded structure.
Multiple connected perforating guns (“perforating gun segments”) are often deployed into the wellbore as a perforating gun string to improve operational efficiency by allowing multiple perforating intervals to be performed during a single deployment (run) into the wellbore. For example and with continuing reference to FIG. 1, the top end 101 of the gun carrier 110 may be connected to an upstream gun carrier 102′ (only the connecting portion of the upstream gun carrier 102′/perforating gun segment is shown in FIG. 1) and the bottom end 102 of the gun carrier 110 may be connected to a downstream gun carrier 101′ (only the connecting portion of the downstream gun carrier 101′/perforating gun segment is shown in FIG. 1) by virtue of respective tandem sub connectors 151 that threadingly connect on opposite sides (as described below) of the tandem sub connector 151 to complimentary threaded portions on each of the successive gun carriers 110, 101′, 102′. For purposes of this disclosure, “downstream” means further into the wellbore and “upstream” means further towards the surface of the wellbore. Electrical signals relayed by, e.g., the conductive line 144 may be transferred between successive gun segments as described below.
In an example shown in FIG. 1 at the bottom end 102 of the perforating gun 100, a first side 152 of the tandem sub 151 connects to the gun carrier 110 of the illustrated perforating gun 100 while a second side 153 of the tandem sub 151 connects to the gun carrier 101′ of the downstream perforating gun. An enlarged circumferential portion 154 of the tandem sub 151 provides a seal between the successive perforating guns. A pressure bulkhead 150 with an electrical feedthrough is housed within the tandem sub 151 and may provide an electrical connection between respective conductive lines in each of the successive perforating guns and/or between a conductive line of the upstream perforating gun and a detonator 155 of the downstream perforating gun. The conductive line 144 may relay an electrical signal along a length L of the perforating gun segment 100 from a top bulkhead feedthrough connection 156 to a bottom bulkhead feedthrough connection 157 and thereby to a successive perforating gun segment for, among other things, initiating selective detonation of a particular perforating gun segment by, e.g., providing a coded digital signal to arm the particular perforating gun segment and an electrical input to activate the detonator of that perforating gun segment and thereby initiate the associated detonating cord. For purposes of this disclosure, “selective detonation” means that each perforating gun in the gun string may be detonated individually and at different times, for example, when a digital signal corresponding to a particular perforating gun segment is received at that perforating gun segment. In use, the perforating gun segments in the gun string must be detonated in a “bottom-up” fashion—i.e., the furthest downstream perforating gun at each interval must be detonated before the others—otherwise the conductive line will be severed between remaining perforating guns.
In view of at least the above considerations, mechanical dimensions and electrical performance must be within tight tolerances to ensure safe and reliable operation of perforating gun segments in gun strings. For example, the position of the internal gun assembly 140 must be precisely set to make proper electrical contact with, e.g., the feedthrough bulkheads 150. In addition, reliable electrical and ground connections and feedthrough properties of conductive components are critical for ensuring that an electrical signal is safely and effectively relayed between contact points on opposing ends of the perforating gun segment. Accordingly, these and other properties of a perforating gun segment may be tested/verified to particular quality specifications before the perforating gun segment is shipped. Typical methods for conducting such measurements may include, for example, manually or digitally measuring physical dimensions of the perforating gun segment and sequentially attaching electrical leads to different electrical (and related) components to measure various electrical properties and logging the results individually. The typical processes may be slow, labor intensive, and susceptible to human error.
For at least the above reasons, devices, systems, and methods are needed for efficiently and accurately measuring and logging physical dimensions and electrical properties of a perforating gun segment.